Gasification of biomass, coal emissions, and other sources of hydrocarbons is a common technique for producing syngas, which may be employed in a variety of downstream uses. Syngas may also be produced by steam reforming of coke. Syngas is often employed for power generation or chemical production. However, syngas generally includes a high content of acid gases (e.g., COS, H2S, and CO2) and other impurities that render the syngas unsuitable for downstream uses. Such impurity-laden syngas is often referred to as sour syngas.
Sour syngas is often subjected to various treatment stages to remove the acid gases and other impurities. Physical solvents (e.g., methanol and dimethyl ether polyethylene glycol) are commonly employed in liquid/vapor phase absorption stages to absorb sulfur-containing species and some carbon dioxide from the syngas, thereby producing an impurity-rich solvent stream and a separated syngas stream that still includes significant amounts of carbon dioxide. The separated syngas stream is fed to a carbon dioxide treatment stage for further removal of carbon dioxide from the separated syngas stream to produce a carbon dioxide vent stream and a treated syngas stream.
Claus units are often employed to recover elemental sulfur from the impurity-rich solvent stream, with the elemental sulfur being usable in various industrial applications and with solvent recovered for further use in the liquid/vapor phase absorption stage (as well as in other separation units). Claus units are multi-stage processing units that include a combustion stage followed by catalytic stages. A concentrated derivative of the impurity-rich solvent is subject to combustion in the combustion stage to produce a combustion gas stream, with elemental sulfur produced and separated from the combustion gas stream. The combustion gas stream also contains other sulfur-containing species that are then converted to elemental sulfur in the catalytic stages.
Claus units generally require an elevated content of sulfur-containing species (e.g., at least 25 weight % of sulfur-containing species) in the feed thereto for purposes of maintaining combustion in the combustion stage. However, the impurity-rich solvent produced by the liquid/vapor phase absorption stages generally has a content of sulfur-containing species that is significantly less than 25 weight %. Thus, the impurity-rich solvent must be further processed through various additional separation stages to remove CO2, thereby producing the concentrated derivative of the impurity-rich sulfur stream. For example, nitrogen stripping and multiple flash columns are often required to increase the proportion of sulfur-containing species in the impurity-rich solvent. Such additional unit operations render sulfur recovery costly and complex.
Accordingly, it is desirable to minimize or reduce various units used for sulfur recovery from an impurity-rich solvent stream produced during sour syngas treatment. It is also desirable to minimize the complexity of sulfur recovery during sour syngas treatment. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.